Memories are generally classified into volatile memories and non-volatile memories, and RRAM is one of the non-volatile memories which can be driven by electric current or voltage and can switch between the high impedance state and the low impedance state so as to store data. In the structure of RRAM, it is composed of a stacked layer of metal-insulator-metal, and the insulator may have reversible switching characteristics. During operations, a pulse voltage is applied to the RRAM to switch its resistance states to perform “data writing” or “data erasing”, and then a small bias is used for capturing current values to determine the impedance state in order to read data.
FIG. 1 is a conventional RRAM 6, which includes two electrode layers 61 spaced apart with each other and made of platinum (Pt) and titanium nitride (TiN), respectively, and a resistance switching layer 62 interposed between the two electrode layers 61 and made of nitroxide silicon oxynitrid (SiON). Then, an endurance experiment is performed on the conventional RRAM 6. That is, an alternate current is applied to the RRAM 6, such that the resistances of the RRAM 6 are continuously switched, and current values in the experiment are recorded and plotted during each switching as shown in FIG. 2. The formation or breaking of a conduction path is occurred in the resistance switching layer 62 during the switching between the high impedance state and the low impedance state; however, because each formation of the conduction path is not fixed, an irregular resistance transition may be occurred. That is, as shown in FIG. 2, the deviations of the solid dots are more obvious, which affects the stability of the RRAM 6.